1. Field of the Invention
The present invention relates generally to blind rivets which may be used to secure two layers of material together with access from one side only, and more particularly concerns an improved blind rivet which drills its own aperture through the two layers of materials and securely attaches the materials together.
2. Description of the Prior Art
Rivets have been used as fastening members for many years, beginning with the use of hot rivets which were inserted through an aperture, and peened. More recently, blind rivets have been used to secure two layers of materials together while requiring access from one side only. Blind rivets are inserted into an aperture from the front side of said layers, and fastened from the same front side. Some blind rivets are equipped at their forward, blind end with a drill bit, whereby rotation of the rivet in one direction produces the requisite holes in the layers of the material to be joined.
One technique for the fastening of blind rivets is that of the so-called "pop" rivet in which a shaft extends through a hollow cylindrical rivet sleeve having an enlarged head thereon. The rivet sleeve is typically made of a material such as aluminum. A mandrel is located on the end of the shaft, and positioned adjacent the blind end of the rivet sleeve. The rivet is inserted into aligned apertures in the joinable layers, and the shaft is placed under tension from the front surface of the uppermost layer to draw the mandrel against the rivet sleeve and toward the head of the rivet sleeve. Such action radially expands the blind end of the rivet sleeve behind the rear surface of the underlying layer.
The shaft is scored near the end attached to the mandrel, and upon the exertion of sufficient tensile force, the shaft will break off at the scored location after the rivet is set. Such blind rivets of the "pop" rivet variety are widely used today in a broad number of applications. Examples of pop rivets of the self-drilling type may be found in U.S. Pat. Nos. 3,935,786; 4,293,258 and 4,998,853. One drawback involving the use of pop rivets is that two separate tools or tool modalities must be employed, namely one tool function which supplies torque for drilling the hole, and a separate tool function which applies a high pulling force on the shaft while bearing against the head of the rivet.
Another technique for the fastening of blind rivets is to use internal threaded means to expand the rivet sleeve adjacent its blind end. Such rivets, of the self-drilling type, are disclosed in U.S. Pat. No. 5,815,906 to Johnson, and U.S. Pat. No. 5,183,357 to Palm, wherein rotation of the rivet in one direction produces the requisite hole, and rotation in the opposite direction achieves fastening of the rivet.
Blind rivets of the type which fasten by threaded means often do not provide securing strength equal to that obtainable by blind rivets of the pop rivet type. Also, self-drilling blind rivets of the type which fasten by threaded means are relatively slow in achieving fastening because of the needed revolutions of the threaded means.
It is accordingly an object of the present invention to provide a self-drilling blind rivet for joining two layers of solid substrate, said rivet having a head extremity and opposite forward extremity expandable by threaded means to achieve fastening of said rivet against said layers.
It is another object of this invention to provide a rivet as in the foregoing object which provides improved fastening strength.
It is a further object of the present invention to provide a rivet of the aforesaid nature wherein said threaded means is fast-acting in achieving expansion of the rivet.
It is a still further object of this invention to provide a rivet of the aforesaid nature which is of simple, rugged construction amenable to low cost manufacture.
These objects and other objects and advantages of the invention will be apparent from the following description.